A Dual Mode MoTe2/WS2/WSe2 Double Van der Waals Heterojunctions Phototransistor for Optical Imaging and Communication

Van der Waals (vdW) heterostructures, formed by stacking different two-dimensional (2D) materials, have emerged as a promising platform for next-generation optoelectronic devices through band engineering. While various all-2D and mixed-dimensional heterojunction phototransistors based on p-n junctions or Schottky junctions have been developed, their performance, often constrained by the trade-off between responsivity (R) and response speed, limits their widespread application. Here, a dual-mode phototransistor based on a MoTe2/WS2/WSe2 double vdW heterostructure is designed. The bottom WSe2 layer effectively modulates the entire MoTe2/WS2 heterojunction channel, enabling both photoconductive and photovoltaic modes with exceptional optoelectronic properties in a single device. Specifically, the proposed device exhibits a maximum R of 2540 A W-1 and an impressive specific detectivity of 8 x 10(12) Jones under the photoconductive mode. Under the photovoltaic mode, it achieves a fast response speed of 35.3/49.1 mu s and a high light on/off ratio of 2 x 10(5). Additionally, the device exhibits latent potential for high-resolution imaging across various wavelengths and fast optical communication. This work offers a rational alternative for achieving dual-mode photodetection and highlights its promising application prospects in imaging and optical communication.